Continuous production process for preparing silicone rubber by gas phase mixing method

Abstract

The invention relates to the technical field of silicone rubber material processing, and discloses a continuous production process for preparing silicone rubber by a gas-phase mixing method, which comprises the following steps: step 1, adding raw silicone rubber, fumed silica, inert gas, a structure control agent and an auxiliary agent into continuous mixing equipment in proportion; step 2, mixing is performed under nitrogen protection, the mixing temperature is controlled to be 40-70 DEG C, and the mixing time is 8-18 minutes; 3, feeding the mixed rubber material into a heat treatment device, and carrying out heat treatment at 160-200 DEG C for 1-1.5 hours; and step 4, feeding the rubber material subjected to heat treatment into at least one multi-screw extruder which is connected in series for dynamic shearing and mixing. Compared with the prior art, the preparation method has the advantages that the fumed silica is introduced in the form of aerosol and is mixed with atomized raw rubber on line, so that efficient and uniform mixing of the filler and the base rubber from the microscopic level is realized, and finally, a silicone rubber product with excellent performance is obtained through continuous heat treatment and dynamic devolatilization.

Description

Technical Field

[0001] This invention relates to the field of silicone rubber material processing technology, specifically to a continuous production process for preparing silicone rubber by gas-phase mixing. Background Technology

[0002] Silicone rubber is a high-performance elastomer with both inorganic and organic molecular chains. It is widely used in aerospace, automotive, electronics, and medical fields due to its excellent high and low temperature resistance, weather resistance, electrical insulation, and physiological inertness. Traditional silicone rubber production processes primarily employ a batch-type internal mixer / kneader process. This involves mixing, kneading, heat-treating (curing), and cooling hydroxyl-terminated polysiloxane raw rubber with reinforcing fillers (such as fumed silica), structure control agents, and other additives in batches within a large kneader, followed by extrusion and devolatilization granulation. This batch-type production process has several drawbacks:

[0003] 1) The production cycle is long, often taking dozens of hours from material input to output, resulting in low efficiency;

[0004] 2) Poor batch-to-batch product quality stability;

[0005] 3) High energy consumption and large equipment footprint;

[0006] 4) During the mixing and heat treatment process, the powdered filler (fumed silica) is prone to flying, resulting in a poor working environment and insufficient wetting with the base rubber, making it difficult to achieve the best reinforcing effect.

[0007] To overcome the shortcomings of batch processes, continuous production has become the industry's development direction. Currently, there have been some attempts to use screw extruders for continuous mixing, but most processes still involve directly and physically mixing all raw materials (raw rubber, powdered fillers, and additives) before feeding them into the extruder. This method fails to fundamentally solve the problem of difficult dispersion and wetting of fumed silica in the base rubber, easily leading to uneven mixing and clumping, affecting the product's mechanical properties and appearance.

[0008] Therefore, it is of great significance to develop a fully continuous production process that can achieve efficient dispersion of fillers, stable product quality, and true continuous production. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to overcome the above-mentioned technical difficulties and provide a continuous production process for preparing silicone rubber by gas phase mixing. By introducing fumed silica in the form of aerosol and mixing it with atomized raw rubber online, the filler and base rubber are efficiently and uniformly mixed at the micro level. Finally, through continuous heat treatment and dynamic devolatilization, a high-performance silicone rubber product is obtained.

[0010] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0011] A continuous production process for preparing silicone rubber by gas-phase mixing includes the following steps:

[0012] Step 1: Add the raw silicone rubber, fumed silica, inert gas, structure control agent and additives to the continuous mixing equipment in proportion;

[0013] Step 2: Mix under nitrogen protection, with the mixing temperature controlled at 40-70℃ and the mixing time at 8-18 minutes;

[0014] Step 3: Send the mixed rubber compound into a heat treatment device and heat treat it at 160-200℃ for 1-1.5 hours;

[0015] Step 4: The heat-treated rubber compound is fed into at least one multi-screw extruder connected in series for dynamic shearing and mixing.

[0016] Step 5: The material after dynamic shearing and mixing is continuously fed into the devolatilization unit, where it is devolatilized under conditions of vacuum degree of -0.08MPa to -0.1MPa and temperature of 150-200℃ to remove low molecular weight volatiles from the material.

[0017] Step 6: After thorough mixing and removal of volatiles, the silicone rubber compound is extruded through an extruder head, granulated, and cooled to obtain the final silicone rubber product.

[0018] Furthermore, the specific surface area of ​​the fumed silica is 150–400 m². 2 / g, the dosage is 20-60% of the mass of the raw silicone rubber.

[0019] Furthermore, the inert gas is nitrogen or argon.

[0020] Furthermore, the structure control agent is one or more of hexamethyldisilazane, hydroxyl silicone oil, diphenylsilanediol, and alkoxysilane.

[0021] Furthermore, the additives include one or more of vulcanizing agents, heat-resistant agents, and antioxidants, or a mixture thereof.

[0022] Furthermore, the heat treatment process is carried out under nitrogen protection, with the nitrogen flow rate maintained at 10 L / min or higher.

[0023] Furthermore, the multi-screw extruder is a twin-screw extruder or a three-screw extruder; the temperature of the dynamic shear mixing process is 80℃~200℃, and the screw speed is 100rpm~1200rpm.

[0024] Furthermore, the cooling process employs water cooling or air cooling, with a cooling time of 5 to 20 minutes.

[0025] Furthermore, the entire continuous production process is carried out continuously in a closed system, with the time from raw material input to finished product output not exceeding 4 hours.

[0026] Furthermore, the silicone rubber product has excellent high and low temperature resistance and can be used for a long time in the range of -60℃ to 250℃.

[0027] The advantages of this invention compared to the prior art are:

[0028] 1. This invention breaks the traditional intermittent production model and realizes integrated continuous operation from raw materials to finished products, resulting in high production efficiency and large capacity.

[0029] 2. In this invention, fumed silica is mixed online with raw rubber under the influence of an inert gas, avoiding problems such as dust dispersion and uneven pre-dispersion. Combined with continuous heat treatment and efficient screw shearing, it ensures extremely uniform filler dispersion and excellent batch-to-batch consistency. The resulting silicone rubber product exhibits excellent high and low temperature resistance and can be used for extended periods within the temperature range of -60℃ to 250℃.

[0030] 3. The present invention has a compact process and high thermal energy utilization efficiency; the entire system is sealed, with no dust leakage, and a good working environment, which meets the requirements of green manufacturing.

[0031] 4. This invention is easy to automate, reducing manual intervention and lowering production costs. Detailed Implementation

[0032] In the description of this invention, unless otherwise stated, "a plurality of" means two or more. Furthermore, the term "comprising" and any variations thereof are intended to cover non-exclusive inclusion.

[0033] The present invention will now be described in further detail with reference to the embodiments.

[0034] Example 1

[0035] A continuous production process for preparing silicone rubber by gas-phase mixing includes the following steps:

[0036] Step 1: Add raw silicone rubber, fumed silica, inert gas, structure control agent, and additives to a continuous mixing apparatus in the specified proportions. The fumed silica has a specific surface area of ​​150 m² / g. 2 / g, the dosage is 20% of the mass of raw silicone rubber. The inert gas is nitrogen. The structure control agent is a mixture of hexamethyldisilazane and hydroxyl silicone oil. The additive is a mixture of vulcanizing agent and heat resistant agent;

[0037] Step 2: Mix under nitrogen protection, with the mixing temperature controlled at 40℃ and the mixing time at 8 minutes;

[0038] Step 3: Send the mixed rubber compound into a heat treatment device and heat treat it at 160°C for 1 hour;

[0039] Step 4: The heat-treated rubber compound is fed into a series of multi-screw extruders for dynamic shear mixing; the heat treatment process is carried out under nitrogen protection, and the nitrogen flow rate is maintained above 10L / min; the multi-screw extruder is a twin-screw extruder or a three-screw extruder; the temperature of the dynamic shear mixing process is 80℃, and the screw speed is 100rpm;

[0040] Step 5: The material after dynamic shearing and mixing is continuously fed into the devolatilization unit, where it is devolatilized under conditions of vacuum of -0.08MPa and temperature of 150℃ to remove low molecular weight volatiles from the material.

[0041] Step Six: After thorough mixing and removal of volatile components, the silicone rubber compound is extruded through an extruder die, granulated, and cooled to obtain the final silicone rubber product. The cooling process uses water cooling or air cooling, and the cooling time is 5 minutes.

[0042] Example 2

[0043] A continuous production process for preparing silicone rubber by gas-phase mixing includes the following steps:

[0044] Step 1: Add raw silicone rubber, fumed silica, inert gas, structure control agent, and additives to a continuous mixing equipment in a specified ratio; the fumed silica has a specific surface area of ​​400 m². 2 / g, the dosage is 60% of the mass of the raw silicone rubber. The inert gas is argon. The structure control agent is a mixture of diphenylsilanediol and alkoxysilane. The additives are a mixture of heat resistant agent and antioxidant;

[0045] Step 2: Mix under nitrogen protection, with the mixing temperature controlled at 70℃ and the mixing time at 18 minutes;

[0046] Step 3: Send the mixed rubber compound into a heat treatment device and heat treat it at 200°C for 1.5 hours;

[0047] Step 4: The heat-treated rubber compound is fed into two multi-screw extruders connected in series for dynamic shear mixing; the heat treatment process is carried out under nitrogen protection, and the nitrogen flow rate is maintained above 10L / min; the multi-screw extruder is a twin-screw extruder or a three-screw extruder; the temperature of the dynamic shear mixing process is 200℃, and the screw speed is 1200rpm;

[0048] Step 5: The material after dynamic shearing and mixing is continuously fed into the devolatilization unit, where it is devolatilized under a vacuum of -0.1MPa and a temperature of 200℃ to remove low-molecular-weight volatiles from the material.

[0049] Step Six: After thorough mixing and removal of volatile components, the silicone rubber compound is extruded through an extruder die, granulated, and cooled to obtain the final silicone rubber product. The cooling process uses water cooling or air cooling, and the cooling time is 20 minutes.

[0050] The entire continuous production process of this invention is carried out continuously in a closed system, with the time from raw material input to finished product output not exceeding 4 hours. The silicone rubber product has excellent high and low temperature resistance and can be used for extended periods within a temperature range of 250°C.

[0051] The present invention and its embodiments have been described above, and this description is not restrictive. If those skilled in the art are inspired by this description and design similar embodiments without departing from the spirit of the invention, such embodiments should fall within the protection scope of the present invention.

Claims

1. A continuous production process for preparing silicone rubber by gas-phase mixing, characterized in that, Includes the following steps: Step 1: Add the raw silicone rubber, fumed silica, inert gas, structure control agent and additives to the continuous mixing equipment in proportion; Step 2: Mix under nitrogen protection, with the mixing temperature controlled at 40-70℃ and the mixing time at 8-18 minutes; Step 3: Send the mixed rubber compound into a heat treatment device and heat treat it at 160-200℃ for 1-1.5 hours; Step 4: The heat-treated rubber compound is fed into at least one multi-screw extruder connected in series for dynamic shearing and mixing. Step 5: The material after dynamic shearing and mixing is continuously fed into the devolatilization unit, where it is devolatilized under conditions of vacuum degree of -0.08MPa to -0.1MPa and temperature of 150-200℃ to remove low molecular weight volatiles from the material. Step 6: After thorough mixing and removal of volatiles, the silicone rubber compound is extruded through an extruder head, granulated, and cooled to obtain the final silicone rubber product.

2. The continuous production process for preparing silicone rubber by gas-phase mixing according to claim 1, characterized in that: The specific surface area of ​​the fumed silica is 150–400 m². 2 / g, the dosage is 20-60% of the mass of the raw silicone rubber.

3. The continuous production process for preparing silicone rubber by gas-phase mixing according to claim 1, characterized in that: The inert gas is nitrogen or argon.

4. The continuous production process for preparing silicone rubber by gas-phase mixing according to claim 1, characterized in that: The structure control agent is one or more of hexamethyldisilazane, hydroxyl silicone oil, diphenylsilanediol, and alkoxysilane.

5. The continuous production process for preparing silicone rubber by gas-phase mixing according to claim 1, characterized in that: The additives include one or more of vulcanizing agents, heat-resistant agents, and antioxidants, or a mixture thereof.

6. The continuous production process for preparing silicone rubber by gas-phase mixing according to claim 1, characterized in that: The heat treatment process is carried out under nitrogen protection, with the nitrogen flow rate maintained at 10 L / min or higher.

7. The continuous production process for preparing silicone rubber by gas-phase mixing according to claim 1, characterized in that: The multi-screw extruder is a twin-screw extruder or a three-screw extruder; the temperature of the dynamic shear mixing process is 80℃~200℃, and the screw speed is 100rpm~1200rpm.

8. The continuous production process for preparing silicone rubber by gas-phase mixing according to claim 1, characterized in that: The cooling process uses water cooling or air cooling, and the cooling time is 5 to 20 minutes.

9. The continuous production process for preparing silicone rubber by gas-phase mixing according to claim 1, characterized in that: The entire continuous production process is carried out continuously in a closed system, and the time from raw material input to finished product output does not exceed 4 hours.

10. The continuous production process for preparing silicone rubber by gas-phase mixing according to claim 1, characterized in that: The silicone rubber product has excellent high and low temperature resistance and can be used for a long time in the range of -60℃ to 250℃.